Agriculture Reference
In-Depth Information
Protists
Protists are the outcasts in the microbe world, their main distinguishing feature seems to
be what they aren't — they're neither bacteria nor fungi nor animals nor plants. You may
be familiar with some such as the amoeba and the paramecium.
Many of them are single-celled, but not all. Sometimes they join up to form wonderfully
gooey slime molds that can actually work together as one, navigating a maze in order to get
to the food hiding at the finish line. The kelp you may have seen washing up on ocean
beaches (an algae now manufactured into one of the most popular organic fertilizers) is ac-
tually a protist, not a plant. Algae produce the majority of the oxygen in this world, so it's
good for us that they are around.
There are also some protists that have given us some problems. Phytophthora causes
blight in potatoes and was a major contributor to the great Irish famine that caused over 1
million people to starve to death in the middle of the 19
th
century. Another Plasmodium
causes malaria in humans.
Despite the unpopular ones, protists are mostly beneficial, and — like us and all other
forms of life — they're just trying to get by. A protozoan can eat 10,000 bacteria in a day.
With 10,000 amoebae per teaspoon of soil, they can eat 100 million bacteria each day. Dur-
ing this process, nitrogen is converted to ammonium, upon which many of your plants will
happily dine. We say that bacteria and fungi
immobilize
nutrients by storing them in their
bodies, and then protists (along with other microbes, plants and animals)
mineralize
these
nutrients — meaning they make them available again, by eating the bacteria and fungi.
Protists also form many symbiotic relationships with bacteria, where each benefits the
other. Protists live in a liquid environment, mostly in the water, but some of them live in
wet soil and have some similar roles to bacteria and fungi. We don't specifically talk about
them all that much in gardening, but when we talk about bacteria and fungi, they're often
implied.
